Assessment of medication use during pregnancy by Web-based questionnaires, pharmacy records and serum screening

Objective: To compare assessment of early pregnancy medication exposure using three methods of data collection. Methods: Serum samples were obtained from 752 women participating in the PRegnancy and Infant DEvelopment (PRIDE) Study before gestational week 17. For 52 women using medication at the date of blood sampling according to Web-based questionnaires or pharmacy records, we analysed serum samples using untargeted liquid chromatography time-of-flight spectrometry. Results: Medication was detected in 18 serum samples (35%). Medications taken orally for chronic conditions reported in the questionnaire were detected in serum and vice versa. Pharmacy records did not identify additional exposed women, but missed exposure in 5 women mainly due to unavailability. We observed substantial discordance between the three methods for inhaled medication, dermatological preparations, and medications for short-term use, which went often undetected in serum. Conclusions: It remains challenging to assess medication use in large-scale studies as no 'gold standard' is currently available.